At the dawn of the last millennium, a European wine connoisseur would have sought fine vintages, as today, in Italy, Germany, and France—but also in England, then dotted with vineyards. Heat-loving beech trees carpeted Europe far into Scandinavia; Viking ships crossed an iceberg-free ocean to ice-free harbors in Greenland and Newfoundland; farmers enjoyed twice-annual harvests of wheat and other grains; and chroniclers recorded a succession of long, glorious summers and mild winters.

All that changed in the mid-twelfth century, when a cooling trend set in over the northern hemisphere. The trend reduced the average annual temperature by only a few degrees, but that was enough to change the face of three continents. Over the next three centuries, England lost its storied vineyards to the cold. In central China, orange groves and mulberry trees froze, chilling a citrus- and silk-based economy that had endured for generations. Glaciers in the Alps, the Himalayas, the Rockies grew by yards, then miles, in just a few years. The Vikings abandoned their colonies in North America when the ground became too hard even to bury the dead.

The effects were disastrous. In a time of reduced crop yields, prices of grain shot up, and for the first time in generations Europe knew famine and malnutrition. What little grain that could be stored developed a cold-tolerant blight called ergot, which, among other effects, produced symptoms of madness—symptoms that were often interpreted as proof of demonic possession. With the gnawing pain of hunger came widespread social unrest, and peasant rebellions and small-scale wars became the norm. At the same time, those powers that could afford the expense mounted expeditions to far-off continents, seeking to establish colonies in warmer climes—and finding, even in the Caribbean, cold waters and depleted shoals and forests wherever they went.

Better times came in the mid-15th century and the arrival of warmer weather, a time that, not coincidentally, brought the period of economic and cultural expansion we now call the Renaissance. That happy time ended a century later in a spasm of religious intolerance, witch-hunting, and warfare, all accompanied by a return of the cold—and, indeed, the arrival of temperatures such as Europe had not seen since the age of the Neanderthals. The Dutch painter Peter Breughel the Elder recorded the onset of that fierce cold snap with his paintings of frozen rivers and swirling armies of half-starved, half-mad villagers, and he was not exaggerating by much: with the advent of the renewed Little Age Ice, as later scholars would come to call it, came extreme storms, drought, the return of famine and civil war, and the desperate search for someone to blame. Thus it was that tens of thousands of Europeans were put to death as witches in the cold decades between 1550 and 1620.

Once again, the political effects were catastrophic; some historians even attribute such events as the French Revolution and the Irish Potato Famine, at least in part, to the cold. Europe saw its worst days in the year 1816, “the year without a summer,” when crops failed throughout the continent. That time is remembered in Mary Shelley’s novel Frankenstein, written during that cold summer; its pages record the creation of a monster who feared only fire and warmth and died in Arctic ice. Bonapartistes warned that the savage cold of 1816 was divine retribution for the defeat and imprisonment of the emperor Napoleon the year before, but the English, who suffered terribly from it, did not yield.

Against the odds, peace held, and, two decades later, warmth returned to the northern hemisphere, beginning an era of higher average temperatures that has persisted to this day.

Climatologists are divided on what caused the Little Ice Age, but most agree that multiple causes, some of them still little understood, were at work. One was the solar phenomenon described by the so-called Maunder minimum, by which a relatively fast rotation of the sun produces few sunspots and therefore reduces the level of solar radiation in the earth’s atmosphere. Another was a cyclical variation in the deep ocean conveyor belt that joins the comparatively warm Atlantic and cold Pacific oceans; with this variation, the temperate Gulf Stream shifted course, and the North Atlantic became so cold that icebergs were commonly sighted as far south as Bermuda. Still another was the effect of intense volcanic activity along the circumpacific seismic belt, with massive eruptions in Alaska, Japan, and Indonesia; the “year without a summer,” 1816, was the result at least in part of the eruption of the 13,000-foot-tall Indonesian volcano Tambora, which blew apart in 1815, losing nearly a mile of its height and killing at least 50,000 people in the immediate vicinity. (On this event, see Jelle Zeilinga de Boer and Donald Sander’s lively book Volcanoes in Human History.) A similar worldwide cooling occurred after the Filipino Mount Pinatubo erupted in 1991, though its effects were far less disastrous and shorter-lived.

Of this, however, scientists are sure: the last Little Ice Age ended as quickly as it arrived, turning from a time of cold and one of temperate weather and increased fertility in only a decade. In an age of rapid global climate change, a time when vineyards are returning to England, can another ice age appear just as suddenly? Stay tuned.